<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 300px;
            height: 40px;
            border: 1px solid pink;
            text-align: center;
            line-height: 40px;
        }
    </style>
</head>
<body>
    <div></div>
    <script>
        const div = document.querySelector('div')
        function getMyDate(){
            const date = new Date()
            let h = date.getHours()
            let m = date.getMinutes()
            let s = date.getSeconds()
            h = h <10 ?'0'+ h :h
            m = m <10 ?'0'+ m :m
            s = s <10 ?'0'+ s :s
            return `今天是：${date.getFullYear()}年${date.getMonth()+1}月${date.getDate()}号${h}:${m}:${s}`
        }
        div.innerHTML = getMyDate()
        setInterval(function(){
            div.innerHTML = getMyDate()

        },1000)
    </script>
</body>
</html>